this is my first major instructable, so we'll see how it goes. (and i'm sorry, i spent a lot of time adding notes to the fotos, and i can still see them in the editor, but they don't seem to be showing up. they help a lot. don't know what i did wrong.)
i find work is fun with the right tools. without them, maybe not so much.
metalwork, at least as much so as anything else. let's consider the simple task of welding basic steel frames in two dimensions...
sure, it can be done with cheesy corner clamps, but slowly. also, the cheesy clamps don't resist the drawing of cooling weld metal very well, so joints end up out of square. no bueno.
an elegant solution is the modular fixturing table. perform a web search for that and you'll see what i mean.
with that, one can clamp virtually anything to a very flat reference surface with great force to prepare for tack welding. then just check the structure, and weld it out. much quicker, easier, and with greater precision and repeatability than corner clamping one joint at a time on an uneven surface.
one problem, those tables are pretty crazy expensive and the fixturing hardware equally so. furthermore, the combination of features i want is not available anywhere i could find.
and here we are. this is an outline of my approach to this problem, presented as a list of things, instead of a hard and fast recipe. my design intent is to combine the designs of two portable/entry level welding tables that are currently available, at lower cost, whilst developing various fabrication skills. your needs or design intent may vary. with luck, this will help.
diy fixturing may follow. the clamps and fixtures for those tables are just as crazy expensive as the tables themselves. i have some ideas for diy versions of several of those fixtures.
Step 1: - Design
design inspiration: probably the first two commercially available portable/entry level tables you'll find in a common web search, hopefully made cheapish by comparison.
desired features / design goals
- more or less portable and easily stored
- folds like an old fashioned tv tray
- heavy, stable and strong enough to support at least 200 pounds
- flat enough for efficient assembly of frames and boxes
- standard holes in a regular grid pattern for versatile fixturing
- exposed ends of tube on the long axis of the frame to provide for expansion of the work surface
as broad a base at the ground as possible
learn and develop additional fab skills
- centered and aligned holes drilled in pipe
- cutting fishmouth joints
- welding round pipe frames
- scratch tig and stick welding practice
- mathematics for project work
new tools to complete the project (the project bonus)
- hardened steel drill guide
- 34 inches tall, good working height for me.
- 80 pounds or less, as i can carry that a fair distance without falling out. even lift it over my head if needed.
Step 2: - Tools and Materials
tools: things that work
- means to weld steel
- mig/tig/stick/oxyfuel welding setup
- 1/8" 7018 is your friend
- ruler, various squares, measuring tape, calipers
- magic marker, paint marker, scriber, soapstone
- hacksaw, portaband, angle grinder w/ cutoff wheel, chop saw
- center punch, hand power drill, drill press, drill bits
- hole saw, angle grinder
- flat assembly surface
- 1/2" steel plate
- c-clamps, f-clamps, vise grip clamps, bench vise
materials: stuff used
- work surface
- 0.220" x 24" x 34" steel plate
- 0.125” x 1” x 105" square tube
- (2) 3/4”x120" steel pipe
- cut to (2) ~28" and (2) 40"
- cross pieces for outer legset.
- 5/16” round stock
- 3/32” hitch pins
Step 3: - the Top
cut the frame members, arrange, clamp, tack, check, weld out.
clamp frame to top plate, tack, check, weld out. i guessed at the weldments, but did put some thought into them. first time ever welding square tube to plate, and worth its imperfection. learned the heat must be turned up pretty high to really get the arc down into the gap to fully butter in top and bottom. not very good all together, but some were damn fine, i'd say. 1/8" 7018 at around 150 amps seemed to do it. i did not weld the joints on the face to mate with the top plate, so i wouldn't have to grind those joints flat. this thing is solid, and yet only 62 pounds. before boring about (80) 1/2" holes in it. the half inch plate i use currently for welding weighs over one hundred all by itself. inconvenient. plus, i just plunk it down on top of a workmate type workstand. meanwhile, i set the new top across two heavy saw horses and stood on it. felt like i was on stage, it was just that solid. measure, mark, and drill holes on grid pattern. the pattern i chose was not precisely square. 3" centers along the short side, more like 3.75" along the long side. this was to make the spacing even, whilst not boring through the frame. after drilling, it weighs about 60 pounds.
Step 4: - the Base
cut the legs to length. (4) 40"
drill 5/16" holes at prescribed locations. precise alignment and centering are critical to smooth assembly and stability. perfection is a journey, not a destination. placement based on the mathematics of the design. centers targeted 21" and 39.375" from bottom ends. in my case, i chose to put the threaded ends of the pipes at the bottom. i figure i might get some end caps later on to screw on to make feet. could work as built in leveling. not sure, tho.
cut and cope cross pieces for inner legset.
tricky part. used 1" hole saw in a benchtop drill press, and carefully went to town, backing up the pipe with a block of wood to catch the saw. i can't imagine trying this with a hand drill. this worked surprisingly well. probably should have used so cutting fluid but didn't. one could also cut it squarely, then cope with a grinder. see metalgeek.com for printable patterns for cutting pipe joints. it's difficult to explain the measurements, because i didn't do that very well myself. basically, i cut and coped one end, cleaned up the burrs, then measured 27.5" to the other end to mark the center of the opposite cope. the measurement was based on fitting up the legs on the top frame, leaving space enough for welding the bracketry on later. a bit of pantseat guesswork here.
cut and drill some pins and spacers for assembly
cut and drill some stock for bracketry
weld inner legset joints.
assemble outer legs to inner legset. and...
Step 5: - Interface
the top attaches to the base with brackets made of scrap 1/4" plate, cut, drilled and dressed.
(8) 1" x 1.25" pieces
on four pieces, 5/16" hole drilled centered on the short axis, 0.75" from the end to be welded to the top frame
assemble the base, including the brackets. tack the brackets in place. check and recheck the fit by removing and replacing the base. get them in the right places, weld out.
weld the bracket pieces with holes outboard from the legs they support. the pieces with no holes, place inboard. when all in place, drill through outer bracket and leg into inner bracket. this is to ensure alignment. this part proved tough to complete. biggest lesson from the entire project... accurate drilling in steel is more difficult than it sounds. thus i decided the regular grid pattern could not be completed with the precision i wanted. a healthy complement of locking c-clamps will have to do. i believe they will. anyway, with luck and a little reaming, the holes will align.
cut (6) 5/16" round pins, (4) at 5", (2) at 4". the five inch pieces pin the legs to the base. the four inch pieces pin the legs together at their pivot points. drill 7/64" (or there abouts) holes into the pins, near the ends, to accept the 3/32" hitch pins. assemble them temp-like, mark the finished length needed, then put them in a vise and pound away to ninety degrees. clearly there are more elegant ways to do this, but whatever.
in the future, i may return to drill the legs all through where they align with the brackets when folded up, as illustrated.
Step 6: Ready for Action
see here, folded and ready to move, then unfolded and ready to rock. the process takes about sixty seconds to complete.
believe me when i tell you, i am extremely pleased with this thing. all together, i think i'm into this for about $80, including some new tools bought to complete it. call that residual value. also, i can stand and jump on the thing, and it feels like a stage riser. solid. i left the threaded pipe ends intact, figuring i could add some caps or something as levelers, but so far i haven't needed them. i estimate the final weight at about eighty five pounds. and the lower cross member is a nice footrest when planted on a stool running tig practice.
of course, there are some things i'd do differently, but i had to build it first to figure them out. I hope this helps someone.